1. Field of the Invention
The present invention relates to a method for producing a toner for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like, and a method and apparatus for producing resin particles.
2. Description of the Related Art
Conventionally, only pulverization methods had been used for producing a toner for developing an electrostatic image (hereinafter, also referred to as simply “toner”) used for electrophotographic recording copiers, printers, facsimiles or hybrids thereof. However, recently, a so-called polymerization method in which a toner is formed in an aqueous medium is widely used, and has come to be more commonly used than the pulverization method. The toner produced by the polymerization method is a so-called “polymerized toner” or “chemical toner”.
This is because toner materials are subjected to polymerization reaction when toner particles are formed or during the process of forming the toner particles. Examples of such polymerization methods in practical use include a suspension polymerization method, an emulsion polymerization method, a polymer suspension (polymer aggregation) method, and ester elongation method.
The toner obtained by the polymerization method has such properties that a small particle diameter can be obtained with ease, a particle size distribution is narrow, and a shape is substantially spherical, compared to the toner obtained by the pulverization method. By using the toner obtained by polymerization method, there is an advantage that a high quality image can be obtained by the electrophotographic system. On the other hand, it also has a disadvantage of being inefficient because the polymerization process requires much time, and toner particles are solidified and separated from the solvent, and then repeatedly washed and dried. The process requires a great deal of time, water, and energy.
There is a known method called the spray dry method in which a liquid formed by dissolving and dispersing a toner composition in an organic solvent (hereinafter also referred to as a toner composition liquid) is microparticulated using various atomizers, and then dried so as to obtain a powder toner (For example, Japanese Patent (JP-B) Nos. 3786034 and 3786035, JP-A No. 57-201248). According to this method, washing and drying can be eliminated because water is not necessarily used. Thus, the disadvantage of the polymerization method can be avoided.
According to the method for producing a toner disclosed in JP-B Nos. 3786034 and 3786035, and JP-A No. 57-201248, droplets ejected from nozzles each have a size corresponding to the nozzle diameter. In this method, the toner composition liquid is atomized so as to form droplets, and the droplets unfavorably aggregate before the formed droplets are dried, and then, the solvent is evaporated in the aggregated state, to thereby obtain a toner. As a result, it has been inevitable that the particle size distribution of the toner becomes broad due to aggregation of droplets, and the particle size distribution of the resulted toner has not been satisfactory.
The method for producing a toner by jet-atomizing disclosed in JP-A No. 2006-293320 has been proposed by the applicant of the present invention in aim of solving the above-described problems, and enables production of a toner having narrow particle size distribution with extremely high production efficiency and energy efficiency because it is not necessary to use a large amount of cleaning liquid and repeatedly separate solvent and particles.
However, the produced toner could have a broad particle size distribution depending on the production conditions. In this method, particularly when the large amount of the toner composition liquid is atomized, the droplets could form aggregates before the formed droplets are dried. This method is not sufficient to stably obtain a toner having a narrow particle size distribution.
When a toner having a broad particle size distribution is used in the electrophotographic system, a high-definition image cannot be obtained. Thus, the production of a toner having a narrow particle size distribution has been keenly demanded.